Flat-panel displays (FPD's) have been developed which utilize liquid crystals (LC) or electroluminescent materials to produce high quality images. These displays are expected to continue to supplant cathode ray tube (CRT) technology in more applications, due to FPDs relatively smaller size and weight. A promising route to large scale high quality liquid crystal displays (LCDs) is the active-matrix approach in which thin-film transistors (TFTs) are co-located with LCD pixels. An advantage of the active matrix approach using TFTs is the elimination of cross-talk between pixels, and the excellent grey scale that can be attained with TFT-compatible LCDs.
One method (spatial color) of producing colored images for flat panel displays is to use an array of primary colored pixels. In a common approach, a pattern of red, green, and blue filters is applied to a surface of an LCD. The display is illuminated with white light, but each pixel controls light of only one primary color.
The spatial color approach may have a coarse or “pixelated” appearance, particularly when displaying primary colors. Within a red area of the image, for example, all the green and blue pixels must be driven to black. Instead of a smooth red area, the observer may perceive a pattern of red dots on a black background.
An alternative method (sequential color) of producing colored images utilizes back lighting from the three primary colors, blue, green, and red. In this system, the display is scanned three times, once for each primary color. For example, to produce color frames at 60 Hz, the active matrix must be driven at a frequency of 180 Hz. At over 180 Hz, visible flicker is reduced. (See U.S. Pat. No. 6,097,352, issued Aug. 1, 2000 entitled “Color Display Panels” incorporated in its entirety herein by reference.)
An advantage of the color sequential system is the higher resolution obtained and reduced pixelation, as each pixel can display full color using three scans. On the negative side of the ledger are image artifacts, called “color breakup”, resulting from the fact that red, green, and blue subimages are presented at slightly different times. Perception of color breakup may be subjective and highly dependent on the sensitivity of the viewer and/or the content of the video signal.